Transcriptional regulator SpxA1a controls the resistance of the honey bee pathogen Melissococcus plutonius to the antimicrobial activity of royal jelly

Royal jelly (RJ), a brood food of honey bees, has strong antimicrobial activity. Melissococcus plutonius, the causative agent of European foulbrood of honey bees, exhibits resistance to this antimicrobial activity and infects larvae orally. Among three genetically distinct groups (CC3, CC12 and CC13) of M. plutonius, CC3 strains exhibit the strongest RJ resistance. In this study, to identify genes involved in RJ resistance, we generated an RJ-susceptible derivative from a highly RJ-resistant CC3 strain by UV mutagenesis. Genome sequence analysis of the derivative revealed the presence of a frameshift mutation in the putative regulator gene spxA1a. The deletion of spxA1a from a CC3 strain resulted in increased susceptibility to RJ and its antimicrobial component 10-hydroxy-2-decenoic acid. Moreover, the mutant became susceptible to low-pH and oxidative stress, which may be encountered in brood foods. Differentially expressed gene analysis using wild-type and spxA1a mutants revealed that 45 protein-coding genes were commonly upregulated in spxA1a-positive strains. Many upregulated genes were located in a prophage region, and some highly upregulated genes were annotated as universal/general stress proteins, oxidoreductase/reductase, chaperons and superoxide dismutase. These results suggest that SpxA1a is a key regulator to control the tolerance status of M. plutonius against stress in honey bee colonies.     

A convenient route for synthesis of 2-isopropyliden-5-methyl-4-hexen-1-yl butyrate, the sex pheromone of Planococcus kraunhiae (Hemiptera: Pseudococcidae), by use of β,γ to α,β double-bond migration in an unsaturated aldehyde

The Japanese mealybug Planococcus kraunhiae (Kuwana) is an important pest which spoils many kinds of fruit in Japan. Because conventional application of insecticides is often ineffective, alternative strategies are being investigated for management of this pest. Recent studies revealed that a pheromone-based technique which interferes with sexual communication, i.e. mating disruption, was promising. However, mating disruption usually requires a substantial amount of a pheromone. I therefore developed a new and convenient route for synthesis of the P. kraunhiae pheromone, 2-isopropyliden-5-methyl-4-hexen-1-yl butyrate (fujikonyl butyrate). First, a commercially available isomer of fujikonol, 2-isopropenyl-5-methyl-4-hexen-1-ol (lavandulol), was oxidized, furnishing the corresponding aldehyde (lavandulal). The β,γ double bond of lavandulal smoothly migrated to the α,β position in the presence of acids, and as a consequence, the corresponding aldehyde of fujikonol (fujikonal) was obtained. Fujikonal was then reduced to fujikonol, which was esterified with butyric acid to give the pheromone of P. kraunhiae. All the reactions were accomplished under very mild conditions (room temperature to 50 °C) with good yields. Moreover, only small amounts of by-products were generated. The synthetic pheromone obtained by this method can be used as a mating disruptant.